A significant percentage of highly trained female athletes develop Hypogonatropic Hypogonadism and secondary Amenorrhea. Since endogenous opiate levels are high in trained athletes and are known to suppress gonadotropins, we postulated that athletic amenorrhea is opiate-mediated. Therefore we measured LH, FSH and prolactin levels in Eumenorrheic and Amenorrheic female Runnes during treadmill tests followed by TRH/GnRH stimulation, both with and without Naloxone-induced opiate blockade.